Noticed this when I was rolling out 1.31.0-wmf.24. Not very noisy, but spikes occasionally.
#0 /srv/mediawiki/php-1.31.0-wmf.24/includes/specials/pagers/BlockListPager.php(171): MWExceptionHandler::handleError(integer, string, string, integer, array, array) #1 /srv/mediawiki/php-1.31.0-wmf.24/includes/pager/TablePager.php(192): BlockListPager->formatValue(string, NULL) #2 /srv/mediawiki/php-1.31.0-wmf.24/includes/pager/IndexPager.php(445): TablePager->formatRow(stdClass) #3 /srv/mediawiki/php-1.31.0-wmf.24/includes/pager/TablePager.php(101): IndexPager->getBody() #4 /srv/mediawiki/php-1.31.0-wmf.24/includes/specials/SpecialBlockList.php(195): TablePager->getFullOutput() #5 /srv/mediawiki/php-1.31.0-wmf.24/includes/specials/SpecialBlockList.php(115): SpecialBlockList->showList(BlockListPager) #6 /srv/mediawiki/php-1.31.0-wmf.24/includes/specialpage/SpecialPage.php(522): SpecialBlockList->execute(NULL) #7 /srv/mediawiki/php-1.31.0-wmf.24/includes/specialpage/SpecialPageFactory.php(579): SpecialPage->run(NULL) #8 /srv/mediawiki/php-1.31.0-wmf.24/includes/MediaWiki.php(288): SpecialPageFactory::executePath(Title, RequestContext) #9 /srv/mediawiki/php-1.31.0-wmf.24/includes/MediaWiki.php(861): MediaWiki->performRequest() #10 /srv/mediawiki/php-1.31.0-wmf.24/includes/MediaWiki.php(524): MediaWiki->main() #11 /srv/mediawiki/php-1.31.0-wmf.24/index.php(42): MediaWiki->run() #12 /srv/mediawiki/w/index.php(3): include(string) #13 {main}